Divide the project into submodule to support also Android, deadline unsettled

We could divide the module into different submodules, and here are the following for the moment

- utils: Contains all the JSON converted and socket interface (only the interface)
- RPC: contains all the socket implementation, and five a ClightningRPC implementation access, (we could support also android)
- plugin: Contains all the interfaces to developing a plugin for c-lightning